Q: Is 400,009 a Prime Number?
A: Yes, 400,009 is a prime number.
A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 400009 can be evenly divided by 1 and 400,009, with no remainder.
Since 400,009 can be divided by just 1 and 400,009, it is a prime number.